The plasma membrane
H+-ATPase plays an important role in the plant response to nutrient and environmental stresses. However, the involvement of plant root plasma membrane
H+-ATPase in adaptation to
phosphate (P)
starvation is not yet fully elucidated. In this study, experiments were performed with soybean roots in low-P nutrient
solution (10 microM). Treatment with
fusicoccin, an activator of the plasma membrane
H+-ATPase, increased P uptake by 35%, while
vanadate, an inhibitor of plasma membrane
H+-ATPase, severely suppressed it. These results suggested that P uptake might be regulated via the modulation of the activity of plasma membrane
H+-ATPase under P
starvation. The relationship between P uptake and the activity of plasma membrane
H+-ATPase was examined further by using plasma membrane
H+-ATPase transgenic Arabidopsis thaliana under low-P conditions. Transgenic plants absorbed more P compared with wild-type Arabidopsis. Results from real-time RT-PCR, western-blotting and immunolocalization analysis indicated that the increase in activity of the plasma membrane
H+-ATPase by P
starvation was caused by its transcriptional and translational regulation. A higher expression was observed at the translational level than at the transcriptional level. P
starvation could induce a transient increase of endogenous
indole-3-acetic acid (IAA) in soybean roots. The exogenous application of IAA stimulated the activity of plasma membrane
H+-ATPase and P uptake, while
naphthylphthalamic acid (NPA), an IAA transport inhibitor, blocked IAA effects. Taken together, these results suggested an involvement of root plasma membrane
H+-ATPase in the adaptation of soybean to P
starvation. IAA might be involved in signal transduction of P
starvation by activating the plasma membrane
H+-ATPase in soybean roots.